PMS: Version 1.12.1.4885 (latest open version)
When I have some movies in my folder and they have an Collections tag, they nicely appear in a folder.
If an other movie should have to be the same Collection Tag, after changing the tag it appears nicely at the other movie in the folder, but the old folder (which is showing 0 movies) doesn’t disappear.
I guess there is a litte bug 2 fix 
Short saying
All Collection folders with no movies in it and showing 0 films, they must not been shown.

Hopefully this will be fixed in the nest public download of PMS
Empty collections are no longer deleted.
You must erase those explicitly.
https://support.plex.tv/articles/201273953-collections/
@OttoKerner said:
Empty collections are no longer deleted.
You must erase those explicitly.
https://support.plex.tv/articles/201273953-collections/
The button “Delete” is missing
@“media.pfjtechnics.nl” said:
The button “Delete” is missing
The linked article mentions explicitly that the delete button only appears if you (temporarily) allow ‘media deletion’.
I recommend you to disable that again, after you are done.
(This is merely a workaround for a bug in the web app. It won’t be necessary after a bugfix has been released.)